Background/Case Studies: Plasma from recovered COVID-19 patients which contain high titres of neutralising antibodies can potentially be used in severely ill COVID-19 patients to reduce symptoms and mortality, as a form of immunotherapy. From Mar-Sept 2020, Singapore had a voluntary COVID-19 Convalescent Plasma (CP) collection programme based in a single centre in central Singapore.
Study
Design/Methods: CP donation eligibility criteria follows Singapore’s strict blood donation eligibility criteria, based on international standards. Standard tests for blood-borne infectious diseases apply. In addition, donors’ plasma must meet a serological qualifying criteria, which was based on a surrogate Virus Neutralisation Test (sVNT), using GenScript cPassTM SARS-CoV-2 Neutralisation Antibody Detection Kit. A plasma dilution of ≥ 1:40 which can still achieve 50% virus neutralisation was arbitrarily set as the criteria for serological qualification. Donors underwent plasmapheresis with the aim to collect 500 ml of plasma. Collected plasma units were sent off-site for flash freezing before being returned to CP programme centre for storage. Donors were pre-medicated with oral calcium supplements. Repeat donors underwent plasmapheresis at least 4 weeks from their last donation.
Results/Findings: From Mar-Sept '20, 160 eligible donors were screened and had their blood taken for eligibility qualification. 131 (81.9%) of the screened donors were disqualified from donation. The majority (80.2% of 131) were disqualified because of insufficient neutralising antibody titres. Other reasons for disqualification included anemia, positive infectious disease screen, poor venous access, travel history and others. Altogether, 33 units of CP were collected from 27 donors. 22 donors made a single successful donation, 4 donors made 2 successful donations and 1 donor made 3 successful donations. There was a decline in the neutralising antibody titre from screening to collection (median interval of 19 days, range 9-91 days) and thereafter from the first collection to subsequent collections.
The most common difficulty encountered during collection of plasma was the premature stoppage of the apheresis procedure due to clotted lines. This occurred most frequently in repeat donors and usually occurred during the return phase of an apheresis cycle. One donor experienced mild hypocalcemia symptoms and one collection was mildly contaminated with red cells.
Out of the 33 units of CP collected, 8 units were used in 7 COVID-19 patients from Apr to Oct 2020. The rest of the collected CP units (75.8%) expired by Sept 2021. Conclusions: The CP screening and collection procedures were resource-intensive, and resulted in a large proportion of screen-failures and subsequent wastages. The lack of evidence showing definite efficacy in the use of CP in COVID-19 patients resulted in the termination of the CP programme for COVID-19 in Singapore 6 months after it started.
Importance of research: CP collected from recovered Covid-19 patients held the promise of being a supplementary treatment for severe COVID-19 patients. Our short experience in CP collection showed the intensity of resources needed, both material and manpower. With the strict eligibility criteria imposed, the CP collection programme had a large proportion of screen-failures. There were also a high proportion of wastages due to expiry as more and more patients were treated with anti-virals and corticosteroids.
